The invention relates to infusion pumps adapted to receive a syringe containing a fluid for infusion via an infusion line, the syringe plunger being displaceable by a suitable drive means, for example an electric motor.
When an infusion pump is in use, particularly in medical applications, it is important that any abnormal increase in pressure in the infusion line should rapidly cause the infusion to cease. Prior art units have either incorporated means, such as a switch, linked to the mechanical drive system and responsive to an unacceptable infusion line pressure, communicated via back-pressure upon the syringe plunger, to operate an electromechanical switch to disable the drive means; or have incorporated a pressure detector in the infusion line acting to produce a signal to disable the drive means in the event of an unacceptable infusion line pressure. The disadvantages of the prior art systems are as follows:
1. in the case of the electromechanical switch coupled to the mechanical drive system, switching is usually slow owing to the need for significant mechanical travel of the system to operate the switch; and
2. in the case of the infusion line pressure sensor, for medical applications the sensor must either be sterilised or replaced for each new infusion duty, as syringes and infusion lines are most usually disposable items.
It is an object of the present invention to provide an infusion pump in which these disadvantages are at least alleviated and preferably substantially overcome.